Coronary heart disease (CHD) mortality has decreased markedly in the United States and several other countries (1). The decline has occured in all four race and sex groups and in most age groups (2). Recent data based on the 1980 census and mortality statistics have demonstrated a substantially greater decrease in the younger are groups, 35-44 (Figure 1). We have noted this same observation in Allegheny County, Pennsylvania data (Table 1). The reasons for the decline in arteriosclerotic heart disease mortality, case-fatality versus incidence, and possible relationship to changes in risk factors, medical care, or early detection are not well documented. It has been extremely difficult to adequately measure the incidence of myocardial infarction (MI) in a community over time. Most studies have been limited to small populations such as in Olsmtead County, Minnesota (3), or occupational groups. A National Heart, Lung and Blood Institute collaborative pilot study of Community Cardiovascular Surveillance is attempting to measure the current CHD morbidity in selected communities. However, this study is dealing with new cases and not attempting to study the trend since 1970. A study of the 35-44 age group, CHD deaths offfers an interesting opportunity to evaluate the CHD trends for the following reasons: 1) Most of the CHD deaths in this age group are group are from fist events, often sudden and therefore may represent incidence of CHD sudden deaths in a community. 2) The deaths are most likely to have either a detailed post-mortem examination or careful diagnostic evaluation. 3) The non-sudden deaths usually occur in a hospital are often first events in this age group and have been well studied. 4) The risk factors for deaths at an early age, are similar to those at other age groups but are often associated with a family history of CHD. 5) The greater decline in CHD mortality in this age group may represent a cohort effect related to evolving changes in risk factors in the United States and other countries.